Snoring and obstructive sleep apnea are typically caused by complete or partial obstruction of an individual's pharyngeal airway during sleep. Usually airway obstruction results from the apposition of the rear portion of the tongue or soft palate with the posterior pharyngeal wall. Obstructive sleep apnea is a potentially lethal disorder in which breathing stops during sleep for 10 seconds or more, sometimes up to 300 times per night. Snoring occurs when the pharyngeal airway is partially obstructed, resulting in vibration of the oral tissues during respiration. These sleep disorders tend to become more severe as patients grow older, likely due to a progressive loss of muscle tone in the patient's throat and oral tissues.
Habitual snoring and sleep apnea have been associated with other potentially serious medical conditions, such as hypertension, ischemic heart disease and strokes. Accordingly, early diagnosis and treatment is recommended. One surgical approach, known as uvulopalatopharyngoplasty, involves removal of a portion of the soft palate to prevent closure of the pharyngeal airway during sleep. However, this operation is not always effective and may result in undesirable complications, such as nasal regurgitation.
A wide variety of non-surgical approaches for treating sleep disorders have also been proposed including the use of oral cavity appliances. It has been previously recognized that movement of the mandible (lower jaw) forward relative to the maxilla (upper jaw) can eliminate or reduce sleep apnea and snoring symptoms by causing the pharyngeal air passage to remain open. Several intra-oral dental appliances have been developed which the user wears at night to fix the mandible in an anterior, protruded (i.e. forward) position. Such dental appliances essentially consist of acrylic or elastomeric bite blocks, similar to orthodontic retainers or athletic mouthguards, which are custom-fitted to the user's upper and lower teeth and which may be adjusted to vary the degree of anterior protrusion.
U.S. Pat. No. 4,901,737, which issued to Toone on 20 Feb., 1990, exemplifies the prior art. Toone discloses an intra-oral appliance for reducing snoring which repositions the mandible in an inferior (open) and anterior (protrusive) position as compared to the normally closed position of the jaw. Once the dentist or physician determines the operative "snore reduction position" for a particular patient, an appropriate mold is taken of the maxillary dentition and of the mandibular dentition for formation of the appliance template. The Toone appliance includes a pair of V-shaped spacer members formed from dental acrylic which extend between the maxillary and mandibular dentition to form a unitary mouthpiece. In an alternative embodiment of the Toone invention, the spacer members are formed in two pieces and a threaded rod is provided to enable adjustment of the degree of mandibular protrusion or retrusion after the mouthpiece is formed.
European patent application No. 0,312,368 published Apr. 19, 1989 also discloses an intra-oral device for preventing snoring. This device consists of a U-shaped mouthpiece which conforms to the upper dental arch of the user and includes a sloped, lower ramp for engaging the mandibular dentition. Normal mouth motions, such as the clenching of the jaw, will cause some of the mandibular dentition to engage the underside of the ramp, thereby camming the lower jaw forward to increase the spacing between the base of the tongue and the posterior wall of the pharynx.
While prior art dental appliances have proven effective in maintaining the mandible in a protruded position to improve airway patency, they often result in undesirable side effects. One of the most common side effects is aggravation of the tempromandibular joint and related jaw muscles and ligaments, especially in individuals who have a tendency to grind their teeth during sleep. Aggravation of the tempromandibular joint has been associated with a wide variety of physical aliments, including migraine headaches. Accordingly, many individuals suffering from sleep apnea and snoring disorders are not able to tolerate existing anti-snoring dental appliances for long periods of time.
The need has therefore arisen for a dental appliance for treatment of snoring and sleep apnea which will maintain the mandible in a preferred anterior position, but which will also allow a limited degree of lateral excursion of the mandible relative to the upper jaw to avoid discomfort to the tempromandibular joint and related muscles and ligaments.